Full Title

Rotary-piston pumps specially adapted for elastic fluids (with fluid ring or the like F04C19/00; rotary-piston pumps in which the working-fluid is exclusively displaced by one or more reciprocating pistons F04B) > of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing > of other than internal-axis type > with toothed rotary pistons > with helical teeth, e.g. chevron-shaped, screw type